ZL50012/GDC ZARLINK [Zarlink Semiconductor Inc], ZL50012/GDC Datasheet - Page 22

• Manufacturer Part Number: ZL50012/GDC
• Description: Flexible 512-ch Digital Switch
• Manufacturer: ZARLINK [Zarlink Semiconductor Inc]

ZL50012
Data Sheet
2.3.7
External High Impedance Control, STOHZ 0 to 15
The STOHZ 0 to 15 outputs are provided to control the external tristate ST-BUS drivers for per-channel high
impedance operations. The STOHZ outputs are sent out in 32, 64 or 128 timeslots corresponding to the output
channels for 2.048 Mb/s, 4.096 Mb/s and 8.192 Mb/s output streams respectively. Each control timeslot lasts for
one channel time.
When the ODE pin is high, the STOHZ 0 - 15 are enabled. When the ODE pin or the RESET pin is low, the STOHZ
0 - 15 are driven high. STOHZ outputs are also driven high if their corresponding ST-BUS outputs are not in use.
Figure 20 gives an example when channel 2 of a given ST-BUS output is programmed in the high impedance state,
the corresponding STOHZ pin drives high for one channel time at the channel 2 timeslot.
By default, the output timing of the STOHZ signals follow the same timing as their corresponding STo signals
including any user-programmed output channel and bit delay and fractional bit advancement. In addition, the device
allows users to advance the STOHZ signals from their default positions to a maximum of four 15.2 ns steps (or four
1/4 bit steps) using Bit 3 to 5 of the Stream Output Control Register (SOCR). Bit 6 in the Stream Output Control
Register selects the step resolution as 15.2 ns or 1/4 data bit. The additional advancement feature allows the
STOHZ signals to better match the high impedance timing required by the external ST-BUS drivers.
FPo
HiZ
SToY
Ch0
Ch1
Ch2
Ch3
Last Ch -2
Last Ch-1
Last Ch
Ch0
Last Ch
STOHZ Y
(Default = No Adv.)
STOHZ Advancement (Programmable in 4 steps of 15.2 ns or 1/4 bit)
STOHZ Y
(With Adv.)
Note: Y = 0 to 15
Output Frame Boundary
Note: Last Channel = 31, 63, 127 for 2.048 Mb/s, 4.096 Mb/s and 8.192 Mb/s mode respectively
Figure 20 - Example: External High Impedance Control Timing
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Zarlink Semiconductor Inc.